Overall quality of instruments
So, every time I add a long note to an instrument, it makes a really irritating vibrating sound that you can hear over all the other instruments. It happens when there's a long note on any instrument and it really destroys the sound. Is that something that I can fix on my own or do I need to wait for an update?
Comments
What version of MuseScore?
What operating system?
What soundfont?
Try https://musescore.org/en/handbook/revert-factory-settings
Could you attach here a score you are having problems with?
It could be you are describing the normal reverb effect that MuseScore uses. You can turn that off if you prefer a drier sound. Go to View / Synthesizer / Master Effects. Or it could be something problem specific to your score or the sounds you are using. As mentioned, in order to understand more, we would need you to atach your score, and describe exactly where the problem you are perceiving is.